The present invention relates to water quality measurement apparatus. More specifically the present invention relates to an improved mechanical arrangement for water quality measurement apparatus.
The use of a plurality of electrochemical sensors deposited on a single wafer for the purpose of measuring multiple parameters of a liquid sample is well known. U.S. Pat No. 5,120,421 discloses an electrochemical sensor which comprises a plurality of multi-element arrays formed on a substrate, the sensor being immersed in a solution for detecting electroactive elements or compounds present in such a solution.
The main advantage of this type of sensor is that it is capable of measuring multiple parameters of a liquid sample. In addition, it is small, cheap to manufacture, and disposable. A primary use for such sensors is for on-line measurements to be made in a mains water pipe, thus eliminating the need to collect a sample and return to the laboratory for analysis, which is costly, time-consuming and often results in substantial errors in measurement accuracy.
To be able to conduct on-line, in-situ type measurements, the sensor must be exposed to the water in the pipe. This is achieved by a known technique in which a specially adapted mechanical device is fitted to the water pipe. This device allows for the sensor to be inserted into the pipe in such a way that the sensing area of the wafer is exposed to the water.
However, this known arrangement suffers from several disadvantages. Firstly the wafer is often inherently thin and may suffer damage or even rupture if exposed to different amounts of pressure. For example, if mains wafer pressure is present on one side of the wafer and atmospheric pressure present on the other side the difference between the two may cause the wafer to rupture. Secondly, any leakage of water from the sensor area to the electrical connectors can result in the sensor failing.
The present invention offers substantial improvements to the known methods in which wafer type sensors are held in place within the mechanical devices used with this type of water monitoring apparatus.
According to the present invention there is provided measuring apparatus including a wafer located between a first and a second xe2x80x98Oxe2x80x99 ring, with said first xe2x80x98Oxe2x80x99 ring being disposed on a first side of side of said wafer, and said second xe2x80x98Oxe2x80x99 ring being disposed on a second side of said wafer, said second side being opposite to said first side, said first and said second xe2x80x98Oxe2x80x99 rings being arranged such that in use a central portion of said first side of said wafer and a central portion of said second side of said wafer being of substantially the same diameter and opposite said central portion of said first side are exposed to substantially equal pressure and any remaining portions of said first and said second sides located outside said central portions are exposed to substantially equal pressure, said apparatus further including a mechanical device arranged to hold said wafer proximate a distal end thereof by means of said first xe2x80x98Oxe2x80x99 ring and said second xe2x80x98Oxe2x80x99 ring, said first and said second xe2x80x98Oxe2x80x99 rings being removably attached to a first and a second xe2x80x98Oxe2x80x99 ring holding means respectively, with said first xe2x80x98Oxe2x80x99 ring holding means being substantially fixed to said distal end of said mechanical device, and said second xe2x80x98Oxe2x80x99 ring holding means being substantially fixed to a detachable block means with said detachable block means being arranged to be held in place at said distal end of said mechanical device such that said wafer is held proximate said distal end of said mechanical device, characterised in that said first xe2x80x98Oxe2x80x99 ring holding means further includes a plurality of pins disposed within a circular area defined by said first xe2x80x98Oxe2x80x99 ring and which corresponds substantially with said central portion of said first side of said wafer, with said plurality of pins arranged to facilitate electrical contact between a plurality of electrical contact points disposed on said first side of said wafer and located within said central portion of said first side of said wafer and further electrical contacts disposed within said mechanical device.
In yet a further embodiment said first xe2x80x98Oxe2x80x99 ring holding means includes a groove into which said first xe2x80x98Oxe2x80x99 ring substantially fits.
In yet a fierier embodiment said second xe2x80x98Oxe2x80x99 ring holding means includes a groove into which said second xe2x80x98Oxe2x80x99 ring substantially fits.
Said plurality of pins may be spring loaded pins.
As will be appreciated by a person skilled in the art, said plurality of pins may be of a type other than spring loaded pin.
According to a further aspect of the present invention said wafer is substantially flat.
According to a further aspect of the present invention said wafer is substantially square.
According to yet a further aspect of the present invention said wafer includes a plurality of sensing devices disposed upon said first side of said wafer.
According to yet a further aspect of the present invention said plurality of sensors are disposed on both said first side and said second side of said wafer.
In yet a further aspect of the present invention said central portions of said wafer are exposed to equal amounts of atmospheric pressure and said remaining portions of said wafer are exposed to equal amounts of water pressure.
In yet a further aspect of the present invention said central portions of said wafer are prevented from being exposed to water.
By exposing each side of the wafer to substantially equal amounts of pressure, the wafer is less likely to rupture due to the effects of unequal amounts of pressure. For example, if the central portion of one side of the wafer was exposed to atmospheric pressure and the central portion of the opposite side was exposed to water pressure, the wafer is more likely to rupture due to the unequal pressure exerted on it then if both sides where exposed to equal amounts of either water or atmospheric pressure.
The apparatus according to the present invention advantageously allows for the wafer to be made thinner, while still being able to be used in applications which expose the wafer to higher pressures. Furthermore, the present invention advantageously allows for sensor devices to be disposed on both sides of said wafer.
While the principle application of the preferred embodiment of the present invention is as a water quality measurement apparatus, as will be appreciated by those skilled in the art, measurement of other types of anlaytes, such as solid, gases and liquids other than water, may be made without departing from the scope of the present invention.